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Weather makes canola more vulnerable to pest damage

This year’s cool, wet conditions in Canada – particularly in Manitoba – are leaving canola crops more vulnerable to pest damage, and thus potential production losses.

Manitoba Agriculture entomologist John Gavloski said the weather has caused canola seed treatments to become less effective, a treatment that contains an insecticide to help fend off flea beetles.

“What is happening is the fields that were planted around mid-May are starting to see the seed treatments wear out," Gavloski said. “The (seed treatments) are not protecting the plant anymore."

Slow crop development is also making this year’s canola crops more vulnerable to flea beetle damage, given that earlier stage crops simply can’t withstand pest pressure as well as later stage crops, Gavloski added.

“Once the canola gets three or four true leaves on its own, it can compensate really well for flea beetle feeding," he said. “But prior to that, when it’s just a couple cotyledons, or one or two true leaves, there’s not enough material there for the plant to really compensate well."

There has already been some spraying in some parts of Manitoba to protect canola crops from flea beetle damage. And, there may need to be more over the next couple weeks until the flea beetles die off, Gavloski said.

“Farmers should look at the number of pits and the feeding damage. If they’re going above about 25% defoliation and there are still a lot of flea beetles around, that’s when we tell them, ‘you may need to consider applying an insecticide.’"

The economic impact of flea beetles on crop production varies with population densities. Yield losses of about 10% are common where flea beetles are abundant, even when the crop is protected with insecticides.

Farmers in Saskatchewan and Alberta have also been dealing with flea beetles this spring, with both striped and crucifer species being present, according to a Canola Council of Canada Canola Watch update.

Flea beetles typically pose the most problems for farmers in the early part of the growing season, but cutworms are also an issue.